Soft aluminum extruders, such as Frontier Aluminum, produce aluminum extrusions that are used as window frames, door frames etc. A metal (iron-based) die is used in the extrusion press. Aluminum is extruded through the die, and the extruded aluminum is cut from the end of the die. Over time, the die of the extruder accumulates a residue of aluminum that obstructs the opening of the die, rendering it unusable. The residue needs to be cleaned from the die for extrusion operations to resume. An approach for cleaning the die is to immerse it in a caustic soda solution of sodium hydroxide to dissolve and remove the aluminum from the die's surfaces.
Typically, the sodium hydroxide solution is held in a tank, where the aluminum is dissolved from the dies. The sodium hydroxide in the solution dissolves the aluminum from the die in a chemical reaction by which the aluminum and the sodium react to form soluble sodium aluminate and hydrogen gas. The more the sodium hydroxide from the solution is consumed and transformed into sodium aluminate, the less effective the solution becomes at dissolving the aluminum from the die. To increase the performance of the caustic solution, the spent caustic solution may be pumped out for disposal as hazardous waste, and the tank is recharged with new chemicals.
An alternative to disposing the spent caustic solution is to regenerate the solution by employing a reaction that extracts the aluminum from the solution, thereby recovering sodium hydroxide from the spent caustic solution.
In one approach, the spent caustic solution may be pumped out and collected for transporting to a fixed chemical treatment plant. Fixed chemical treatment plants, generally stated, require infrastructure in that a containment berm at a minimum must be constructed and fixed tanks and equipment installed inside the containment berm. The installation of a fixed chemical treatment system typically includes pouring and curing a concrete berm, and then installing and anchoring the tanks and equipment inside the containment area.
One disadvantage to this approach is the need to pump out and to transport the spent caustic solution to the chemical treatment plant. Another disadvantage is the need to construct the chemical treatment plant. There is a need for an approach to regenerate caustic solutions that do not have such disadvantages.